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Cost-effectiveness of biologics for moderate-to-severe psoriasis from the perspective of the Swiss healthcare system

European Journal of Dermatology. Volume 19, Numéro 5, 494-9, September-October 2009, Clinical report

DOI : 10.1684/ejd.2009.0725

Summary

Auteur(s) : Roger-Axel Greiner, Lasse R Braathen , Carl-Keller-Weg 17, DE-79539 Lörrach, Germany, Dermatological University Clinic, Inselspital, CH-3010 Berne, Switzerland.

Illustrations

ARTICLE

Auteur(s) : Roger-Axel Greiner¹, Lasse R Braathen²

¹Carl-Keller-Weg 17, DE-79539 Lörrach, Germany
²Dermatological University Clinic, Inselspital, CH-3010 Berne, Switzerland

accepté le 15 Avril 2009

Psoriasis is a chronic, immune-mediated inflammatory disease characterized by periods of remission and exacerbation [1]. Disease prevalence is approximately 2% of the world’s population [2], and about 25% of those individuals have moderate-to-severe psoriasis, which corresponds to 38,000, 4 million, and 1.5 million individuals in Switzerland, Europe, and the United States, respectively. Though rarely life-threatening, psoriasis is associated with significant physical and emotional morbidity and the impact on patients’ quality of life is comparable to other major clinical diseases such as rheumatoid arthritis or cancer [3].

In Switzerland, treatment with biologic therapies for moderate-to-severe psoriasis was initiated in 2004. The tumor necrosis factor inhibitors etanercept, infliximab, and adalimumab as well as the T-cell-targeted therapies alefacept and efalizumab had received Swissmedic approval (but Efalizumab was withdrawn, EMEA 19 February 2009, Swissmedic 20 February 2009). Since production of biologics is cost intensive and resources are finite, compulsory health insurance in Switzerland currently limits treatment to 12 weeks for non-responders. Thereafter, the treating specialist determines responders who can continue treatment and selects a treatment change for non-responders. At present, it is unclear whether costs, risks, and efficacy of one intervention might outweigh those of another. Thus, there is a need for a cost-effectiveness analysis that first evaluates the single interventions used to treat psoriasis and then investigates the potential treatment sequences due to the limitation of the compulsory health insurance. Therefore, this study computed two analyses with the objectives of: i) examining the cost-effectiveness of the biologics in terms of ICER per PASI 50, 75, or 90 responder at 12 weeks; and to: ii) analyzing the ICER per PASI responder at 36 weeks with an elementary model that accounted for the Swiss compulsory health insurance limitation.

Materials and methods

Study population

The study population consisted of subjects with moderate-to-severe psoriasis who had not responded to, or who were intolerant of, other systemic therapies such as cyclosporine, methotrexate, and psoralen/UV light, or, in whom these treatments were contraindicated.

Costs

The cost perspective relied on direct medical costs. Total treatment costs of biologics consisted of drug acquisition costs (i.e. medication, administration, and monitoring) and costs incurred by adverse events. Costs were calculated by multiplying single resource parameters with the corresponding unit cost.

The unit costs of utilized resource parameters (i.e. all drugs and services rendered to the patient) were assessed according to official Swiss prices and tariffs adjusted to the year 2006. The public price for drugs was derived from the Spezialitaetenliste [4]. Outpatient services were costed according to the Swiss official medical tariff structure [14]. Inpatient services due to adverse events were estimated according to Swiss all patient diagnosis related groups (APDRG) [15]. Lab services were priced according to the official list of analyses [25].

Resource utilization

Resource utilization of medication, administration, and monitoring was derived from the official medical prescription label information and from a literature analysis [4]. All drugs and services rendered to the patient were listed for a therapy length of 12, 24, or 36 weeks. The doses of biologics administered were as follows: infliximab (5 mg/kg administered intravenously [IV] at 0, 2, 6 weeks, and thereafter every 8 weeks), etanercept (50 mg subcutaneous [SC] twice weekly [tw] for 12 weeks, then 25 mg SC tw), adalimumab (80 mg SC at week 0, then 40 mg every other week), efalizumab (1 mg/kg once weekly SC), and alefacept (15 mg once weekly intramuscularly [IM] for 12 weeks and then 12 weeks break). The weight of psoriasis patients was stipulated in categories of 4.1%, < 50 kg; 44.5%, 50-69 kg; 42%, 70-89 kg; and 9.4%, ≥ 90 kg, based on the official primary statistics for the general population of Switzerland [6]. Monitoring included diagnostic procedures (X-ray thorax, tuberculosis test, blood cell test, CD4 T-lymphocyte test, urea test) and visits to physicians (physical examination and follow-up consultations). Administration costs were calculated for the IV and IM therapies, infliximab and alefacept, respectively, whereas SC injections of etanercept, adalimumab, and efalizumab were self-administered by the patient. Frequency of severe adverse events, which met the criteria of inpatient treatment, were estimated from a literature analysis and linearly broken down to the time horizon of 12 and 36 weeks: malignancies [7-9], tuberculosis [7, 9, 10], infections [9-11], haematological side effects [9, 12, 13], and in addition injection/infusion site reactions, which required outpatient treatment only [7, 9, 13]. The kind and number of resources utilized, the corresponding unit costs, actual cost, and total treatment cost at 36 weeks are listed in table 1.
Table 1 Number of resources utilized (n), unit cost, cumulated cost, and total treatment cost of continuous treatment for responders at 36 weeks in CHF

	Unit cost	Infliximab		Etanercept		Adalimumab		Efalizumab		Alefacept		Reference
	[CHF]	[n]	Cost	[n]	Cost	[n]	Cost	[n]	Cost	[n]	Cost
Medication	–^*	6	23,855	72	23,436	20	20,022	36	15,018	24	29,967	[4, 24]
Physician visits (drug administration)	188	6	1,130	0	0.00	0	0.00	0	0.00	24	^§	[14, 24]
Monitoring
Physical examination by specialist	86.9	1	86.9	1	86.9	1	86.9	1	86.9	1	86.9	[14, 24]
Follow-up consultations	57.5	2	114.9	2	114.9	2	114.9	4	229.9	4	229.9	[14, 24]
X-ray thorax	90.9	1	90.9	1	90.9	1	90.9	0	0.0	0	0.0	[14, 24]
Mycobacterium tuberculosis	81.0	1	81.0	1	81.0	1	81.0	0	0.0	0	0.0	[14, 25]
Hematogram II (incl. erythrocytes, thrombocytes)	13.5	0	0.0	0	0.0	0	0.0	5	67.5	0	0.0	[14, 25]
Hematogram V (incl. differential leucocytes)	27.0	0	0.0	0	0.0	0	0.0	3	81.0	0	0.0	[14, 25]
Ureat	14.4	0	0.0	0	0.0	0	0.0	3	43.2	0	0.0	[14, 25]
CD4 T-lymphocyte	27.0	0	0.0	0	0.0	0	0.0	0	0.0	18	486.0	[14, 25]
Severe adverse events
Malignancies
Lymphoma	11,256	0.0011	12.7	0.0005	5.6	0.0014	16.0	0.0008	9.4	0.0011	12.0	[7-9, 15]
Neoplasia	4,640	0.0048	22.2	0.0041	18.9	0.0051	23.7	0.0131	60.7	0.0019	8.7	[7-9, 15]
Lower respiratory infection and tuberulosis
Tuberculosis	2,398	0.0005	1.2	0.0001	0.3	0.0018	4.4	0.0000	0.0	0.0000	0.0	[7, 9, 10, 15]
Pneumonia	6,343	0.0148	93.9	0.0138	87.2	0.0139	88.2	0.0042	26.9	0.0019	11.9	[7, 9, 10, 15]
Interstitial pneumonitis	7,463	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0008	5.8	0.0000	0.0	[7, 9, 10, 15]
Skin and soft tissue infection	7,255	0.0086	62.5	0.0080	58.1	0.0081	58.8	0.0049	35.9	0.0021	15.5	[9-11, 15]
Bone and joint infection	7,787	0.0050	38.6	0.0046	35.9	0.0047	36.3	0.0007	5.5	0.0000	0.0	[9-11, 15]
Urinary tract infection	4,217	0.0033	13.9	0.0031	12.9	0.0031	13.1	0.0000	0.0	0.0000	0.0	[9-11, 15]
Sepsis	9,072	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0021	19.2	0.0000	0.0	[9-11, 15]
Herpes zoster virus	4,094	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0014	5.8	0.0000	0.0	[9-11, 15]
Upper respiratory tract infection	3,039	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0007	2.1	0.0005	1.6	[9-11, 15]
Peritonitis or appendicitis	8,886	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0007	6.3	0.0008	7.1	[9-11, 15]
Gastroenteritis	3,678	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0007	2.6	0.0005	2.0	[9-11, 15]
Hepatitis	5,265	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0007	3.7	0.0003	1.4	[9-11, 15]
Inflammatory arthritis	11,314	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0046	52.5	0.0000	0.0	[9-11, 15]
Bronchiolitis obliterans	8,476	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0004	3.3	0.0000	0.0	[9-11, 15]
Aseptic meningitis	4,159	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0008	3.2	0.0000	0.0	[9-11, 15]
Idiopathic hepatitis	7,657	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0004	3.0	0.0000	0.0	[9-11, 15]
Sialedenitis	3922	0.0000	0.0	0.0000	0.0	0.0000	0.0	0.0004	1.5	0.0000	0.0	[9-11, 15]
Other serious infection	3,777	0.0065	24.7	0.0061	22.9	0.0061	23.2	0.0028	10.7	0.0013	5.0	[9-11, 15]
Haematological side effects	12,861	0.0000	0.6	0.0000	0.0	0.0000	0.0	0.0030	38.7	0.0000	0.0	[9, 12, 13, 15]
Injection site reactions	10	0.0671	0.7	0.0000	0.0	0.0000	0.0	0.0025	0.0	0.0000	0.0	[7, 9, 13, 14]
Total treatment cost			25,629		24,052		20,660		15,824		30,835

^aCosts per medication are for Infliximab CHF 3976, Etanercept CHF 483 and CHF 237 (50 mg and 25mg dose), Adalimumab CHF 1001, Efalizumab CHF 417, and Alefacept CHF 1249.

^§Costs of i.m. administration are included in monitoring visits.

Clinical efficacy

The Psoriasis Area Severity Index (PASI) was used to document therapeutic efficacy of biologics, since the PASI is the most frequently cited measure of treatment effectiveness for moderate-to-severe psoriasis and is often employed as the primary outcome measure for clinical trials [16, 17]. Response was defined as achieving primary trial endpoints of PASI 50, 75, or 90, meaning a reduction of at least 50%, 75%, or 90% in the PASI. Table 2 summarizes the placebo-adjusted responder rates at weeks 10-14 (infliximab at week 10, alefacept at week 14, all others at week 12) and at week 24, which were gathered from double-blind, randomized, placebo-controlled clinical trials (RCTs) [5, 18-23, 27].
Table 2 Placebo-adjusted PASI 50, PASI 75, and PASI 90 response rates at 12 and 24 weeks

	12 weeks			24 weeks
	PASI 50	PASI 75	PASI 90	PASI 50	PASI 75	PASI 90
Infliximab	83.2	77.8	55.8	82.1	78.4	57.0
Etanercept^*	68.0	46.4	20.1	63.0	50.9	29.3
Adalimumab	62.0	56.0	24.0	59.0	61.5	42.0
Efalizumab	41.3	23.0	4.2	52.7	39.5	14.4
Alefacept	25.0	16.0	NA	22.0	20.0	NA

^*Etanercept 24 weeks: PASI 50 and PASI 90 were achieved with 50 mg twice per week during 24 weeks.

Cost-effectiveness analysis

In the first part of this analysis, ICER for each biologic was calculated for a treatment duration of 12 weeks without therapy change as the ratio of total cost of treatment minus cost of placebo (estimated to CHF = 0) divided by the corresponding placebo-adjusted responder rates of PASI 50, 75, and 90. This resulted in ICERs to gain one PASI 50, PASI 75, and PASI 90 responder after 12 weeks.

In the second part, a decision tree model was developed (using TreeAge Software, Inc., MA, USA) that reflected the limitation of the Swiss compulsory health insurance (figure 1). Accordingly, the model described the potential treatment sequences of the 5 biologics with a chance node at week 12 over a time horizon of 36 weeks (details in the legend of figure 1). The base case analysis used the same efficacy rates of RCTs regardless of application as initial therapy or as treatment change. Sensitivity analyses comprised a 25% and a 50% reduction of PASI 75 response for the treatment change of non-responders and the variation of total treatment costs as well as of the response rates for the initial therapies by ± 25%. Costs and benefits were not discounted since the time horizon of the model was 36 weeks.

Results

Clinical efficacy

Table 2 shows the placebo-adjusted response rates for PASI 50, PASI 75, and PASI 90 after 12 and 24 weeks for the 5 biologics. The best efficacy was achieved with infliximab, which showed the highest PASI 50, 75, and 90 responder rates measured after 12 and 24 weeks. The second best efficacy was shown by adalimumab; etanercept followed with far lower PASI 75 and PASI 90 rates than infliximab and adalimumab. Efalizumab showed lower efficacy rates than the tumor necrosis factor inhibitors, but increasing from 12 to 24 weeks. The efficacy rates of alefacept were the lowest among the 5 biologics.

Cost-effectiveness

After 12 weeks, ICERs per responder increased in parallel with ascending PASI measure from PASI 50 to PASI 90 for all biologics. The ranking of ICER per PASI 50 responder was efalizumab (CHF 13,040), adalimumab (CHF 13,277), infliximab (CHF 15,427), etanercept (CHF 17,562), and alefacept (CHF 61,477); per PASI 75 it was adalimumab (CHF 14,921), infliximab (CHF 16,505), efalizumab (CHF 22,050), etanercept (CHF 25,748), and alefacept (CHF 96,057). Regarding the ICER per PASI 90 infliximab was most cost effective (CHF 22,995) followed by adalimumab (CHF 34,815), etanercept (CHF 59,407), and efalizumab (CHF 128,979). Considering the increasing strictness of outcome measure from PASI 50 to PASI 90 there was in parallel an increasing advantage in ICERs for biologics with high response rates, particularly for infliximab. Recently, a cost-effectiveness threshold of USD 33,600 per PASI 35 responder was assessed [26]. Adapting this threshold to CHF 35,000 per PASI 50 responder (1USD = 1.04 CHF on 25 June 2008) would mean that 4 of the 5 biologics, excepting alefacept, fulfilled this requirement.

Cost-effectiveness model

In the base-case analysis of the cost-effectiveness model infliximab and adalimumab generated the lowest ICERs at 36 weeks (figure 2). Adalimumab and infliximab achieved CHF 29,254 and CHF 29,826 per PASI 75 responder. Efalizumab, etanercept and alefacept came to CHF 32,771, CHF 35,299 and CHF 48,762 per PASI 75 responder, respectively. One-way sensitivity analyses showed that the variation of total treatment costs had a strong impact, changing the response rates of the initial treatment had a moderate impact, while varying the response rates of the treatment change had a relatively small impact on the ICERs at 36 weeks (table 3). However, these analyses did not substantially affect the outcomes of the cost-effectiveness model and confirmed the robustness of the model in all cases, with lowest ICERs for infliximab and adalimumab followed by higher ratios in the ranking efalizumab, etanercept, and alefacept.
Table 3 Sensitivity analyses. Impact of variation of total treatment cost (cost) and response rates at 12 (Eff12wk) and at 36 weeks (Eff36wk) on ICERs of base case

	Base case	Cost –25%	Cost +25%	Eff12wk –25%	Eff12wk +25%	Eff36wk –25%	Eff36wk –50%
Infliximab	29,826	22,369	37,282	34,649	26,090	30,663	31,548
Etanercept	35,399	26,549	44,249	39,046	32,290	38,959	43,316
Adalimumab	29,254	21,940	36,567	33,196	26,004	31,375	33,828
Efalizumab	32,771	24,578	32,369	35,004	30,730	38,778	47,481
Alefacept	48,762	36,571	60,952	50,125	47,469	60,039	78,101

Discussion

This is the first study to examine the cost-effectiveness of all biologics approved in Switzerland for the treatment of moderate to severe psoriasis in the framework of the compulsory health insurance.

This study has limitations due to scarce epidemiological and economic data available on patients with moderate to severe psoriasis. This analysis focused on direct costs. Indirect costs (i.e. travel, productivity) can be substantial with psoriasis. Dropout rates, which could be as high as 50%, were not considered in the model. The randomization of non-responders to one of 4 other treatment regimens after 12 weeks was essential in order to make the five initial options of biologics comparable. However, in real life, the specialist has to select the appropriate alternative for non-responders individually. Treatment effectiveness was evaluated solely on the basis of PASI, which is the most frequently cited measure of treatment effectiveness for moderate-to-severe psoriasis and is often used as the primary outcome measure in clinical trials across targeted treatments [16, 17]. Indices such as the global assessments of improvement, quality of life, and duration of remission are used in other studies and are also sensitive to patient preferences and response to therapy. Notwithstanding that a treatment response of PASI 50 after 12 weeks might be used in daily routine, the use of PASI 75 in this study appears to be warranted because it was the most common primary endpoint in clinical trials [31, 21-23].

Recently, a meta-analysis presented PASI 75 rates after 8 to 16 weeks of 4 biologics excluding alefacept [28]. These data coincide with the corresponding response rates of the biologics used in this study, in which infliximab is most efficacious followed by adalimumab, etanercept, and efaluzimab. Another meta-analysis compared the pooled relative risks of PASI 75 from RCTs for 4 biologics with placebo without considering adalimumab [29]. The study showed that the decreasing rank order for the pooled efficacy was infliximab, etanercept, efaluzimab and alefacept, which is consistent with our results. In a German study, the ICER of intermittent therapy with etanercept versus non-systemic therapy was estimated at 45,491 EUR per quality-adjusted life year [30]. In another economic evaluation of systemic therapies vs. supportive care, infliximab provided the most benefit due to the highest incremental QALYs, while adalimumab was more cost effective [32].

In conclusion, this study suggests that, from a clinical-economical point of view and given the limitation of the Swiss compulsory health insurance system, it is best value for money if the initial biological therapy with a high response rate is selected, e.g. infliximab, rather than starting with therapies of lower response rates.

Acknowledgements

Financial support: This study was supported by Essex Chemie AG, Luzern, Switzerland. Conflict of interest: None.

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